The Berlusconi era is limping towards a farcical conclusion as the billionaire mogul inflicted upon himself one of the worst humiliations of his 20-year political career.

In a jaw-dropping U-turn, the tycoon voted to support the Italian coalition government after campaigning for weeks to bring it down.

In the hours ahead of the confidence vote in the Senate, former Italian premier Silvio Berlusconi had said he would pull the plug on the government of Enrico Letta because of the former’s opposition to an impending rise in VAT. Most observers said the real reason was Mr Berlusconi’s fury at a vote planned for tomorrow which could strip him of his Senate seat following his tax fraud conviction in August.

However, the media tycoon and three-time premier was forced into a U-turn when it became clear that dozens of senators from his normally supine PDL party (People of Freedom) said they were ready to vote “yes” in the confidence vote.

The rebellion was led by the Deputy Prime Minister and Interior Minister Angelino Alfano, national secretary of Berlusconi’s party who was once seen as a protégé.

There was stunned silence when Berlusconi stood in the senate to announce that he would vote with Premier Letta.

“We have decided to vote for confidence, not without internal disputes,” Berlusconi said. “This is not a U-turn”. He held his head in his hands after he spoke.

There were some gasps and guffaws, but mostly stunned silence in the chamber as Berlusconi made his climb down, with Premier Letta shaking his head.

Just 24 hours earlier, the ex-premier has that it would be “unthinkable” to back the Letta government. But by noon, dozens of senators from the mogul’s centre-right grouping had said they would form a break-away centre-right party and support the left-right coalition government as it sought to introduce electoral reforms and measures against Italy’s spiralling unemployment.

The Pdl senator Robert Formigoni, announced ahead of the vote that he and around 35 of his centre-right colleagues would back Letta in the confidence vote in defiance of Berlusconi.

“It’s not an ideal government,” he said. “But it’s better that than a devastating crisis that hits businesses and Italian families. We remain on the centre-right but we are collaborating with our traditional enemies because there is this extraordinary crisis.”

Mr Letta, who had been tipped to win with just a handful of votes just minutes before Berlusconi’s U-turn, ended up sweeping the vote with a crushing majority of 235 senators in favour and 70 against.

The new lease of life for Mr Letta’s fragile left-right coalition calmed the markets and increased Italy’s chances of emerging from the economic doldrums, pundits said. Though whether the government will achieve the deep reforms and painful tax and budget measures needed to reverse a decade of economic stagnation and cut Italy’s two trillion euro debt remains to be seen.

Yesterday, however, it was the fate of former leader Berlusconi, who was forced to step down in November 2011 at the height of Italy’s financial crisis, that gripped the country.

For the tycoon to try to wreck the Letta Government, only to have to support it at the last moment amid a rebellion in the ranks of the party he founded, there was widespread ridicule; commentators across the spectrum suggested his time as major political force was at an end.

Francesco Specchia, from the right-wing Libero newspaper, said: “In calling this confidence vote, for the first time ever, Berlusconi got his strategy completely wrong.”

Giacomo Marramao, a politics professor at Roma Tre University, said: “I think we are seeing the final chapter of Berlusconi’s political life.”

After the confidence vote passed, the Prime Minister said: “Today is a historic day, we have clearer conditions that let us look far ahead.”

Laura Puppato, a senator in Mr Letta’s centre-left Democratic Party, said: “We hope we are coming to the end of the era where government was run for the business and personal interests of one person.”

Berlusconi, 77, is due to begin a one-year sentence of either house arrest or community service this month following his tax fraud conviction.